Trauma to the diaphyseal segment or the distal segment of the femur may result in simple or complex fractures that require treatment by surgical means. Typically, a metal pin or plate is used to reduce the fracture and stabilize the bone while healing occurs.
For example, one method of treating distal femur fractures utilizes an intramedullary nail (or, alternatively, an IM pin or rod) which is inserted into the bone marrow canal and span a fracture in the bone. Such IM nails are designed to share the load with the bone and to assist with aligning and stabilizing the bone. In some such IM nail systems one or more screws or bolts are used to prevent movement of the nail with respect to the bone in an attempt to maintain proper alignment while the fracture heals. Most commonly, one screw or bolt is positioned below the fracture (near the distal end of the bone), while another screw or bolt may be positioned above the fracture. FIG. 1 shows an illustrative prior art intramedullary nail system.
Alternatively, locked plate systems have been used to treat bone fractures. Such locked plate systems typically comprise a plate that lies outside and against the bone, with at least two clusters of bone screws passing through holes in the plate and into the bone. One of the screw clusters attaches to the bone above the fracture, while another screw cluster attaches to the bone below the fracture. At least some of the holes in the plate are threaded, and at least some of the bone screws have threaded “heads” that engage the threaded plate holes to “lock” the screws to the plate. When the screws are tightened the plate is “locked” to the bone above and below the fracture, thus providing the desired fracture reduction and stabilization. FIG. 2 shows an illustrative prior art locked plate fixation system.
Neither the prior art intramedullary nail systems nor the prior art locked plate systems provide an optimal fixation system for many long bone fractures. While the intramedullary nail systems may be relatively easy to use, the reduction and stabilization they provide may not be optimal since the nail typically has limited contact with the distal portion of the bone. While locked plate systems may provide improved contact with the bone, they may be difficult to align and are generally less easy to use. Additionally, locked plate systems have a biomechanical disadvantage since they are offset relative to the axis of the bone they are attempting to stabilize.
It can be seen from the above that a need exists for improved methods and devices to secure distal fixation of long bones that allows for early functional range of motion without loss of alignment or fixation. The present invention addresses that need.